RU2192425C2 - Method of synthesis of n-phosphonomethylglycine and its salts - Google Patents

Abstract

FIELD: organic chemistry, chemical technology, herbicides. SUBSTANCE: invention relates to method of synthesis of N-phosphonomethylglycine and its salts that are highly effective commercial herbicide useful for control of enormous variety of weeds. Invention describes method of synthesis of N- phosphonomethylglycine and its salts involving mixing aminomethylphosphonate, alkaline metal cyanide or hydrogen cyanide and formaldehyde to yield product followed by hydrolysis of product and isolation of hydrolyzed product with formation of N-phosphonomethylglycine or its salts. Reagents are mixed simultaneously and in the process of formation of the mentioned product regulation of pH value is not required. EFFECT: improved method of synthesis, simplified technological process. 22 cl, 1 tbl

Description

BACKGROUND OF THE INVENTION
N-phosphonomethylglycine, also known by its common name glyphosate, is a highly effective commercial herbicide (marketed under the trademark Roundup ^™ ), useful for controlling a huge variety of weeds. When used in the herbicidal composition, N-phosphonomethylglycine usually takes the form of one of the many salts in solution, preferably in an aqueous solution.

There are many known methods for producing M-phosphonomethylglycine, including several methods for producing N-phosphonomethylglycine from aminomethylphosphonic acid (AMPK) or its salts. These methods include a process in which AMPA is added to an aqueous solution of glyoxal at 40-45 ^{° C.} and heated as described in Japanese Patent Application Laid - Open 61992/1987; a process in which AMPA and glyoxal are reacted in the presence of sulfur dioxide, as described in European patent EP 81459 and US patent 4369142; a method in which AMPA and glyoxylic acid are reacted, and then hydrogen is reduced in the presence of a palladium catalyst, as described in EP 186648; a method in which AMPA and chloroacetic acid are heated in the presence of an acid acceptor, such as sodium hydroxide, as described in Polish patent 120759 and Spanish patent 504479; a method in which AMPA and diethyl bromomalonate are reacted under alkaline conditions, and then hydrolysed under acidic conditions using sulfuric acid, as described in Spanish Patent 545456. These methods, however, have drawbacks involving the use of volatile gases, creating high levels of content waste by-products, inadequate yield of the final product, relatively high material costs and poor product quality.

 Other known methods for the preparation of N-phosphonomethylglycine from AMPA include hydrolysis of the intermediate N-phosphonomethylglycinonitrile or its salts. For example, according to US Pat. No. 4,221,583, AMPA is reacted sequentially with formaldehyde, usually in the presence of alkali, and alkali metal cyanide at pH 7-10. The resulting product, N-phosphonomethylglycinonitrile, is then converted to N-phosphonomethylglycine. The yield of isolated N-phosphonomethylglycine, based on AMPA, was approximately 60% only, and it was necessary to use up to 2.4 times the molar equivalent of potassium cyanide and carefully adjust the pH to achieve this yield.

 Similarly, according to Polish Patent 156,933, the reaction of AMPA to produce N-phosphonomethylglycinonitrile is sequential and multi-stage, using formaldehyde and alkali metal cyanide or hydrogen cyanide. The Polish patent process 156,933 requires even more careful pH control by adding mineral acid to obtain optimal yields.

 PCT / 95 / GB 2573 also relates to the reaction of AMPA to produce N-phosphonomethylglycinonitrile in a sequential, multi-stage process using formaldehyde and alkali metal cyanide. The PCT / 95 / GB 2573 process avoids the use of hydrogen cyanide (HCN) and also requires careful pH adjustment by continuously adding mineral acid to obtain optimal yields.

 US patent 5453537 describes another method for producing N-phosphonomethylglycine using AMPA as the starting compound. AMPA is reacted in the form of its alkali metal double salt and glyconitrile, and the resulting N-phosphonomethylglycinonitrile is hydrolyzed to produce N-phosphonomethylglycine. In accordance with the examples, the yield of isolated N-phosphonomethylglycine was 78% at best, based on AMPA. The nature of AMPA requires for this method the addition of an alkali metal hydroxide in an amount two times the molar amount of AMPA in order to carry out the reaction between glycolonitrile and AMPA. The use of glycolonitrile to obtain intermediate N-phosphonomethylglycinonitrile in this process also eliminates the direct cyanomethylation of AMPA by using more basic, more readily available and less expensive raw materials such as formaldehyde and sodium, potassium or hydrogen cyanide.

 Thus, there is a need at the present level of technology to create a universal method that directly and easily converts AMPA to N-phosphonomethylglycine and its salts in high yields from inexpensive and affordable raw materials.

SUMMARY OF THE INVENTION
The present invention relates to a method for producing N-phosphonomethylglycine and its salts. More specifically, the present invention relates to a method for producing N-phosphonomethylglycine, comprising the reaction of AMPA, alkali metal cyanide or hydrogen and formaldehyde and hydrolysis of the product of this reaction with the formation of N-phosphonomethylglycine and its salts.

 The method according to the present invention has significant advantages compared to other methods for producing N-phosphonomethylglycine, including cyanomethylation of AMPA, which consists in the fact that it does not need to carefully monitor the pH value. In particular, it is not necessary to add mineral acid to the reaction solution AMPA / alkali metal hydroxide / alkali metal cyanide or hydrogen / formaldehyde in order to adjust the pH. The use of alkali metal or hydrogen cyanide reagents and formaldehyde in the AMFC cyanomethylation process of the present invention also allows the reaction to be carried out without the use of the previously prepared glyconitrile reagent used in some other methods. In addition, the method according to the invention is not limited to reagents in the form of alkali metal cyanides, as it can use hydrogen cyanide (HCN) as a cyanide reagent.

Description of Illustrative Embodiments
The present invention is broadly directed to the cyanomethylation step of AMPA in the preparation of N-phosphonomethylglycine.

 In a preferred embodiment, the method of the invention relates to the reaction of AMPA, about one equivalent of an alkali metal hydroxide, about one equivalent of an alkali metal cyanide or hydrogen, and about one equivalent of formaldehyde, followed by the addition of about one equivalent of an alkali metal hydroxide and subsequent acidification of the mixture to crystallize the final glyphosate product.

According to another preferred embodiment, the method of the invention includes a continuous process, in which AMPK and about one equivalent of an alkali metal hydroxide (the mixture of which forms an AMPK monosol), about one equivalent of hydrogen cyanide or an alkali metal and about one equivalent of formaldehyde are added to the reactor with approximately the same the molar ratio over a period of time, for example, about 40-50 minutes, the mixture is maintained at a low temperature, for example, about 5 ^o C or lower. The reaction solution is then stirred, for example, for about 30 minutes at about 3-5 ^{° C.} and then stirred at ambient temperature for a period of time, for example, about 1.5 hours. Then, approximately one equivalent of alkali metal hydroxide is added to the solution. and the solution is heated, for example, for about 2 hours. Then the solution is cooled and acidified to a pH at which the glyphosate product crystallizes, for example, to approximately pH 1.05, and the crystallized glyphosate product is removed by filtration. tration or centrifugation.

According to yet another preferred embodiment, the method according to the invention comprises a batch process, in which an AMPK monosol (which can be obtained by mixing AMPK and an equivalent of an alkali metal hydroxide) and an equivalent of an alkali metal cyanide or hydrogen are mixed in an aqueous solution in a reactor, to which for a period of time equivalent of formaldehyde solution is added, while the temperature is maintained below about 25 ^o C., after which the solution was stirred at ambient temperature for a period of time, for example, for about 1-3 hours. After that, approximately one equivalent of alkali metal hydroxide is added to the mixture, and the mixture is heated to reflux for a period of time, for example, equal to 1-3 hours The solution is then cooled and acidified to a pH such that the glyphosate product crystallizes, for example, to approximately pH 1.05, and the crystallized glyphosate end product is removed by filtration or centrifugation.

 The reagent "AMPK" generally represents aminomethylphosphonic acid or its salt, also called "aminomethylphosphonate". For example, AMPA may be a mono- or double salt of an alkali metal and aminomethylphosphonic acid. In a preferred embodiment, the reagent AMPK is an alkali metal monosol and AMPK, for example, the monosodium or monopotassium salt of AMPK, which can be obtained by mixing aminomethylphosphonic acid with an equivalent of alkali metal hydroxide. For example, the monosodium salt of AMPA can be obtained by mixing AMPA and the equivalent of sodium hydroxide, alone or in the presence of other reagents, such as alkali metal cyanide, or hydrogen, or formaldehyde.

 The cyanide reagent may be an alkali metal cyanide, for example sodium or potassium cyanide, or hydrogen cyanide. The formaldehyde reagent may be added as formalin. The reagents AMPA / alkali metal cyanide or hydrogen / formaldehyde are preferably added in a molar ratio of about 1: 1: 1. When the AMPA component is a mixture of aminomethylphosphonic acid and alkali metal hydroxide, the molar ratio of aminomethylphosphonic acid / alkali metal hydroxide / alkali metal cyanide or hydrogen / formaldehyde is approximately 1: 1: 1: 1. In this context, a ratio of approximately 1: 1 preferably denotes a molar ratio of 0.75-1.25: 1, more preferably a molar ratio of 0.85-1.15: 1, and most preferably a molar ratio of 0.9-1.1 :1.

 The following examples are provided to demonstrate preferred embodiments of the invention. One skilled in the art will appreciate that the techniques described in the examples below represent the techniques described by the inventors for practicing the present invention, and thus may be considered preferred. However, it will be understood by those skilled in the art in light of the present description that many changes may be made in the particular described embodiments, and the results will still be the same or similar without departing from the spirit and scope of the present invention.

Example 1
A three-necked flask with a capacity of 250 ml, containing 25 ml of water, was cooled in an ice bath and was equipped with a thermometer, a mechanical stirrer and two pumps with syringes. One pump had two syringes. A solution of sodium cyanide (4.9 g, 0.1 mol) in 14 ml of water was introduced into one of them, while the second contained 37% ACS brand formalin (0.1 mol) in 14 ml of water. A 60 ml syringe was installed on another pump. This syringe was used to add AMPA in the form of a monosodium salt obtained from AMPK (11.1 g, 0.1 mol), dissolved in 60 ml of water with granules of sodium hydroxide (0.1 mol) at ambient temperature, with monosodium salt of AMPK the solution was slightly warmed to maintain solubility.

Syringe pumps were driven simultaneously. Thus, three reagents were transferred to the flask at approximately the same molar ratio for 40-50 minutes, and each syringe was rinsed with 2 ml of water. The temperature during the addition was maintained at 5 ^{° C.} or lower for most of the addition. The reaction solution was then stirred at a temperature of from 3 to 5 ^o C for about 30 minutes and then at room temperature for about 1.5 hours

An aliquot of the reaction mixture in 1.0 ml was weighed to the fourth digit and diluted with water in a 10 ml volumetric flask. Phosphorus NMR of this diluted sample was carried out using 5% H ₃ PO ₄ as the external coaxial standard. The chemical shifts of AMPK and N-cyanomethyl AMPK (i.e., N-phosphonomethylglycinonitrile) were 19/1 and 16.2 million dollars. in relation to phosphoric acid in the presence of 3.0 equivalents of NaOH. In this case, the bis-cyanomethylated derivative of AMPK was attributed in the form of a shoulder at the peak of N-cyanomethyl - AMPK at 16.4 million dollars. With two equivalents of NaOH, chemical shifts of N-cyanomethyl - AMPK and unreacted AMPK were observed in the regions of 14.9-15.0 and 15.9-16.2 million dollars. respectively. The results of NMR analysis showed a yield of N-phosphonomethylglycinonitrile of 94.6%.

 Sodium hydroxide granules (100 ml) were added to the solution. The resulting yellow solution was then heated under reflux for 2 hours with evolution of ammonia.

 After cooling to ambient temperature, a 1.0 ml aliquot of the hydrolyzate was weighed to the fourth decimal place and diluted with water in a 10 ml volumetric flask. The resulting solution was analyzed by 31P NMR. The chemical shifts of AMPA, glyphosate, and GI in these hydrolyzate samples were 18.7–18.9, 15.9–16.2, and 15.4–16.1 million, respectively. in relation to phosphoric acid. NMR results showed a yield of 94.6%.

The yellow hydrolyzate was transferred to a 250 ml calibrated flask, weighed and concentrated in vacuo on a rotary evaporator at 50-65 ^o C, depending on pressure. The concentrated hydrolyzate was weighed, transferred back to the original flask, and the weight was adjusted by adding water so that a total amount of concentrated hydrolyzate of approximately 65 g was obtained. The concentrated hydrolyzate was mechanically mixed, cooled in an ice bath and treated with three portions of 37% HCl to achieve pH in acidified a solution of 1.05. After crystallization, the suspension was stirred at room temperature overnight, and the pH was periodically adjusted by adding small amounts of concentrated 37% HCl or an aqueous solution of NaOH (40 or 50 wt.%) To bring the pH to 1.05 ± 0.05. If the pH remained within this pH range for at least one hour, crystallization was considered to be complete.

The suspension was filtered into an agglomerated glass funnel mounted on a 250 ml calibrated flask with a vacuum filter. The initial filtrate was reused to rinse the flask and ensure complete solid phase transfer. The filtered solid was washed successively with 10 ml of water and 10 ml of methanol. The wet solid phase was dried in a vacuum oven at 45-55 ^° C until the weight of the solid phase became constant. The dried solid and filtrate were analyzed for glyphosate by HPLC. The yield of isolated glyphosate was 85.3% with a purity of 98.8%.

Example 2
A three-necked 250-ml flask was cooled in an ice bath and was equipped with a thermometer, a mechanical stirrer and a pump with two syringes. In one of them, a solution of sodium cyanide (4.9 g / 0.1 mol) in 14 ml of water was taken, while the second contained 37% ACS grade formalin (0.1 mol) in 14 ml of water. AMPA monosodium salt (0.1 mol) in 60 ml of water was loaded into a 250 ml flask and at the same time solutions of formaldehyde and sodium cyanide were added at a rate of 0.6 ml / min at 3-5 ^° C. The reaction mixture was then stirred at 3-5 ^o With, and then at room temperature, as presented in example 1.

 Phosphorus NMR analysis of this sample in accordance with example 1 showed a yield of N-phosphonomethylglycinonitrile of 93.7%.

 Hydrolysis, acidification with HCl and the isolation of the solid phase of glyphosate were carried out as described in example 1. NMR analysis showed a yield of N-phosphonomethylglycine 91.1%. The yield of isolated glyphosate was 82% with a purity of 100%.

Example 3
The procedure of Example 2 was repeated, except that the flask was loaded with granules of sodium hydroxide (75 mmol) and AMPA (100 mmol) in 60 ml of water instead of the monosodium salt of AMPK and sodium hydroxide (125 mmol) was added to conduct hydrolysis.

 Phosphorus NMR analysis of this sample in accordance with Example 1 showed a yield of N-phosphonomethylglycinonitrile of 51.2%. NMR results showed a yield of N-phosphonomethylglycine 56.8%. The yield of isolated N-phosphonomethylglycine was 40.8% with a purity of 50%.

Example 4
The procedure of Example 2 was repeated, except that granules of sodium hydroxide (125 mmol) and AMPA (100 mmol) were loaded into the flask in 60 ml of water instead of the monosodium salt of AMPK and sodium hydroxide (75 mmol) was added to conduct hydrolysis.

 Phosphorus NMR analysis of this sample in accordance with example 1 showed a yield of N-phosphonomethylglycinonitrile of 80.2%. NMR results showed an 80.6% yield of N-phosphonomethylglycine. The yield of isolated N-phosphonomethylglycine was 67% with a purity of 92%.

Example 5
To obtain an aqueous mixture of sodium cyanide and formaldehyde, a three-necked 50-ml flask was equipped with a magnetic stirrer, a thermometer and a 10-ml plastic disposable syringe, driven by a pump. A solution of sodium cyanide (4.9 g; 0.1 mol) mixed with a magnetic stirrer in 15 ml of milli-Q water in a flask was cooled in an ice bath to 5 ^° C. ACS grade formalin solution (37%, 7.5 ml, 0, 1 mol) was added dropwise from a syringe at a rate of 0.2 ml / min, while the temperature was maintained in the range from 5 to 10 ^o C. At the end of the addition, the solution was cooled and stored at 5 ^o C.

The 250-ml three-necked flask was equipped with a mechanical stirrer, a Y-adapter with a thermometer, a syringe pump with a 20-ml syringe and a reflux condenser. A mechanically mixed suspension of AMPA (11.1 g, 0.1 mol) in 60 ml of water was cooled in an ice bath and treated with the indicated number of granules of sodium hydroxide (100 mmol). Granules of sodium hydroxide were dissolved with stirring, and the resulting solution was cooled to 5 ^o C.

The aqueous mixture of sodium cyanide and formaldehyde obtained above was added to the AMPA solution obtained above using a pump with a syringe at a speed of about 0.6 ml / min, while maintaining the temperature below about 5 ^o C. At the end of the addition, the reaction mixture was stirred at 3 -5 ^o C for another 30-45 minutes The ice bath was removed and the slightly colored reaction mixture was stirred for an additional 90-100 minutes at room temperature. Phosphorus NMR analysis showed a yield of N-phosphonomethylglycinonitrile of 94.1 and 100% in two separate passes.

 The hydrolysis, HCl acidification, and the isolation of the glyphosate solid phase from these experiments were the same as those described for Example 1. The NMR results showed N-phosphonomethylglycine yields of 94.9% and 93.1% in two passes. The corresponding yields of the isolated glyphosate were 84.1% and 81.9% with a corresponding purity of 98.7% and 95.4%.

Example 6
The procedure of Example 5 was repeated, except that the granules of sodium hydroxide (100 mmol) were dissolved in an aqueous mixture of sodium cyanide and formaldehyde, and no additional sodium hydroxide was added to conduct hydrolysis. Phosphorus NMR analysis showed a yield of N-phosphonomethylglycinonitrile of 51.8%. NMR results showed a yield of N-phosphonomethylglycine 73.7%. The corresponding yield of isolated glyphosate was 56.9% with a purity of 69.7%.

Example 7
The procedure of example 6 was repeated, except that instead of the monosodium salt of aminomethylphosphonate, AMPK (100 mmol) was used, and sodium hydroxide (100 mmol) was additionally added to conduct hydrolysis. Phosphorus NMR analysis showed a yield of N-phosphonomethylglycinonitrile of 93.0%. NMR results showed a yield of N-phosphonomethylglycine of 92.6%. The corresponding yield of isolated glyphosate was 79.6% with a purity of 94.7%.

Examples 8 to 13
The procedure of Example 5 was repeated, except that the number of granules of sodium hydroxide used to dissolve the AMPA before adding to the reaction flask and the additional amount of sodium hydroxide added for hydrolysis varied, as shown in the table, together with the results of such variations.

Example 14
In accordance with the procedure of example 1, disodium salt of AMPA obtained in 60 ml of water from AMPA (11.1 g, 0.1 mol) and granules of sodium hydroxide (0.2 mol) was used instead of its monosodium salt.

 Phosphorus NMR analysis of the reaction mixture corresponding to Example 1 showed a yield of N-phosphonomethylglycinonitrile of 54.6%.

 Hydrolysis was carried out as described in example 1, except that sodium hydroxide was not added. Acidification with HCl and isolation of the solid phase of glyphosate were carried out as described in Example 1. NMR analysis showed a yield of N-phosphonomethylglycine 71.3%. The yield of isolated glyphosate was 54.8% with a purity of 69.6% according to analysis.

Example 15
A 250 ml three-necked flask was equipped with a thermometer, a mechanical stirrer and a pump with a syringe containing 37% ACS grade formalin (0.1 mol) in 7.5 ml of water. The monosodium salt of AMPA (0.1 mol) and sodium cyanide (4.9 g; 0.1 mol) in 120 ml of water were loaded into a 250-ml flask and stored at a temperature of less than 5 ^o C. Formaldehyde was added at a rate of 0, 2 ml / min. The reaction mixture was then stirred at 3-5 ^o C and at room temperature, as shown in example 1.

 Phosphorus NMR analysis of this sample in accordance with Example 1 showed a yield of N-phosphonomethylglycinonitrile of 94.1%.

 Hydrolysis, acidification with HCl and the isolation of the solid phase of glyphosate were carried out as described in example 1. NMR results showed a yield of N-phosphonomethylglycine 96.7%. The yield of isolated glyphosate was 86.7% with a purity of 100.0%.

Example 16
The procedure of Example 15 was repeated, except that the monosodium salt of AMPA (0.1 mol) and sodium cyanide (0.1 mol) were introduced into the flask and stored at an ambient temperature of 25 ^o C. Formaldehyde was added at a rate of 0.2 ml / min at 25 ^o C. the Reaction mixture was then stirred at ambient temperature, as shown in example 1.

 Phosphorus NMR analysis of this sample in accordance with Example 1 showed a yield of N-phosphonomethylglycinonitrile of 82.8%.

 Hydrolysis, acidification with HCl, and isolation of the glyphosate solid phase were carried out as described in Example 1. NMR results showed a yield of N-phosphonomethylglycine of 97.3%. The yield of isolated glyphosate was 81.5% with a purity of 95.7%.

Example 17
The procedure of Example 15 was repeated, except that the monosodium salt of AMPA (0.1 mol) and sodium cyanide (0.1 mol) were loaded into a flask in 60 ml of water and left at a temperature of less than 5 ^o C. Formaldehyde was added at a rate 0.2 ml / min. The reaction mixture was then stirred at 3-5 ^o C and at room temperature (ambient temperature), as shown in example 1.

 Phosphorus NMR analysis of this sample in accordance with example 1 showed a yield of N-phosphonomethylglycinonitrile of 89.6%.

 Hydrolysis, acidification with HCl, and isolation of the glyphosate solid phase were carried out as described in Example 1. NMR results showed a yield of N-phosphonomethylglycine of 93.4%. The yield of isolated glyphosate was 80.5% with a purity of 94.8%.

Example 18
A 250-ml three-necked flask was equipped with a thermometer, a mechanical stirrer and a pump with a syringe containing an aqueous solution of sodium cyanide (4.9 g; 0.1 mol) in 12 ml of water. The monosodium salt of AMPA (0.1 mol) in 60 ml of water and 37% formalin ACS (0.1 mol) in 7.5 ml of water were loaded into a 250 ml flask and left at a temperature of less than 5 ^o C. A solution of cyanide sodium was added at a rate of 0.32 ml / min. The reaction mixture was then stirred at 3-5 ^o C and at room temperature, as shown in example 1.

 Phosphorus NMR analysis of this sample in accordance with Example 1 showed a yield of N-phosphonomethylglycinonitrile of 79.4%.

 Hydrolysis, acidification with HCl, and isolation of the glyphosate solid phase were carried out as described in Example 1. NMR results showed a yield of N-phosphonomethylglycine of 79.0%. The yield of isolated glyphosate was 67.0% with a purity of 92.4%.

Example 19
The 250-ml three-necked flask was equipped with a mechanical stirrer, a thermometer and a pump with a syringe. A solution of sodium cyanide (4/9 g; 0.1 mol) mixed with a magnetic stirrer was added in 35 ml of milli-Q water and cooled in an ice bath to 4 ^o C. A drop was added from a syringe at a rate of 0.2 ml / min 37% formalin solution ACS (7.5 ml; 0.1 mol) while maintaining the temperature in the range of 5-10 ^o C.

In a separate 125 ml Erlenmeyer flask, a suspension of AMPA (11.1 g; 0.1 mol) mixed with a magnetic stirrer in 60 ml of water was cooled in an ice bath and treated with sodium hydroxide (100 mmol) to give a solution of the monosodium salt of AMPA. The ice bath was removed and the slightly colored solution was allowed to warm to room temperature. The solution was added to the flask at 5 ^{° C.} using a pump with a syringe at a flow rate of approximately 1.3 ml / min. The reaction mixture was then stirred at 5 ^{° C.} or lower for 1/2 hour and then at room temperature for 1.4 hours.

 Phosphorus NMR analysis of this sample in accordance with Example 1 showed a yield of N-phosphonomethylglycinonitrile of 95.6%.

 Hydrolysis, acidification with HCl, and isolation of the glyphosate solid phase were carried out as described in Example 1. NMR results showed a yield of N-phosphonomethylglycine of 94.2%. The yield of isolated glyphosate was 82.4% with a purity of 96.7%.

 All methods described and claimed can be carried out without undue experimentation in the light of the present description. Although the composition and methods of the present invention have been described in view of preferred embodiments, it will be apparent to those skilled in the art that modifications can be made to the method described herein without departing from the concept, spirit, and scope of the invention. It is understood that all such similar replacements and modifications obvious to those skilled in the art are encompassed by the spirit, scope and concept of the invention.

Claims (22)

 1. A method of producing N-phosphonomethylglycine or its salts, comprising mixing aminomethylphosphonate, alkali metal cyanide or hydrogen cyanide and formaldehyde to obtain a product, hydrolyzing the obtained product and isolating the hydrolyzed product to obtain N-phosphonomethylglycine or its salts, characterized in that the mixing of the reactants is carried out at the same time, during the formation of said product, essentially no pH adjustment is required.  2. The method of claim 1, wherein the aminomethylphosphonate is an aminomethylphosphonic acid monosol.  3. The method of claim 2, wherein the aminomethylphosphonic acid monosalt is a monosodium or monopotassium salt.  4. The method of claim 1, wherein the alkali metal cyanide is potassium cyanide or sodium cyanide. 5. The method according to p. 1, in which the reaction of aminomethylphosphonate, alkali metal cyanide or hydrogen cyanide and formaldehyde is carried out at a temperature not exceeding 60 ^o C.  6. The method according to p. 1, in which formaldehyde is used in an amount of from about 0.75 to 1.25 times the molar amount with respect to aminomethylphosphonate.  7. The method of claim 1, wherein the alkali metal cyanide or hydrogen cyanide is used in an amount of about 0.75 to 1.25 times the molar amount with respect to the aminomethylphosphonate.  8. The method according to claim 1, in which the aminomethylphosphonate is aminomethylphosphonic acid, mono-alkali metal aminomethylphosphonate or alkali metal aminomethylphosphonate.  9. The method of claim 1, wherein the aminomethylphosphonate is a reaction product of aminomethylphosphonic acid and an alkali metal hydroxide.  10. The method of claim 9, wherein the alkali metal hydroxide is sodium hydroxide or potassium hydroxide.  11. The method according to p. 9, in which the alkali metal hydroxide is used in an amount of from about 0.75 to 1.25 times the molar amount with respect to aminomethylphosphonic acid.  12. The method according to p. 1, in which to conduct hydrolysis add mineral acid.  13. The method according to p. 1, in which N-phosphonomethylglycine is obtained after hydrolysis by adding alkali metal hydroxide or strong mineral acid in an amount sufficient to achieve a pH of about 1.0-1.2.    14. The method of claim 1, wherein the aminomethylphosphonic acid, alkali metal hydroxide, formaldehyde and alkali metal cyanide or hydrogen cyanide are added simultaneously.  15. The method of claim 1, wherein the alkali metal aminomethylphosphonate, formaldehyde and alkali metal cyanide are added simultaneously.  16. The method of claim 1, wherein the alkali metal aminomethylphosphonate, formaldehyde and hydrogen cyanide are added simultaneously.  17. A method of producing N-phosphonomethylglycine or its salts, comprising mixing aminomethylphosphonate, an alkali metal cyanide or hydrogen cyanide and formaldehyde to obtain a product, hydrolyzing the obtained product and isolating the hydrolyzed product to obtain N-phosphonomethylglycine or its salts, characterized in that the mixture is mixed simultaneously at least two of the reagents of aminomethylphosphonate, alkali metal cyanide or hydrogen cyanide and formaldehyde, after which other reagents are added to obtain a product, for example and this during the formation of the said product essentially does not require pH adjustment.  18. The method of claim 17, wherein the alkali metal formaldehyde and hydrogen cyanide or hydrogen cyanide are mixed simultaneously and then reacted with aminomethylphosphonic acid.  19. The method of claim 18, wherein the aminomethylphosphonic acid is further reacted with an alkali metal hydroxide.  20. The method according to p. 17, in which formaldehyde, alkali metal hydroxide and aminomethylphosphonic acid are mixed simultaneously and then reacted with alkali metal cyanide or with hydrogen cyanide.  21. The method of claim 17, wherein the alkali metal cyanide or hydrogen cyanide and formaldehyde are mixed together at the same time and then reacted with a mono-alkali metal aminomethylphosphonate.  22. The method of claim 17, wherein the alkali metal cyanide, alkali metal hydroxide and aminomethylphosphonic acid are mixed simultaneously together and then reacted with formaldehyde.

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